Twenty years after publication of the previous version, the new and completely revised version of the US diagnostic system of psychiatric disorders, the Diagnostic and Statistical Manual of Mental Disorders – DSM-5, was introduced in 2013. Over the course of its preparation, which took many years, current knowledge was summarized and the respective consequences for the classification and diagnosis of psychiatric disorders were discussed in groups of high-ranking experts. In many regards, DSM-5 does not fulfil the original plans and expectations; however, for the most part it can be seen as an acceptable summary of current knowledge on mental disorders. Although universities and research groups throughout the world have shown great interest in DSM-5, in countries outside the USAthe ICD-10 is still the mandatory classification system, until the official introduction of the ICD-11. From many perspectives, DSM-5 can be seen as a kind of predecessor model for ICD-11. However, ICD-11, despite the original plan for it to be very similar to DSM-5, will find many of its own solutions. This paper presents some important issues on DSM-5 that will be of interest to clinicians working in the field of mental disorders. In addition, it uses some examples to illustrate how DSM-5 operationally defines some disorders and how it differs from ICD-10 and DSM-IV.